Urban growth, once characterized by the gradual development and expansion of suburbs, has taken on a new form. Today's "cities" have become sprawling metropolitan regions. For example, the metropolitan region of Chicago expanded by 47 percent between 1970 and 1990. It now extends into eight counties and three states. Surprisingly, the regional population increased only four percent (1).

As the quantity of natural and agricultural landscape surrounding cities decreases, so too does habitat quality. Habitats have been reduced, altered, and isolated; native plant communities are disappearing, wetlands are being displaced, and impervious cover is causing flooding.

SPOT XS satellite image

Satellite imagery can be analyzed to identify habitat and factors affecting habitat quality.

The SPOT XS satellite image on the left can be analyzed to understand the transition from rural to urban land cover conditions.

SPOT XS Multispectral Satellite Image
Date of image: June 27, 1996
Image bands displayed: 3,2,1 in RGB
Spatial resolution: 20 meters

Land cover conditions

The land cover map on the left produced from the SPOT XS image shows urban growth (red) encroaching on forest areas (dark green).

Primary forestland habitat 

Primary habitats represent essential land cover types that a species needs to survive. These habitats, such as the forestland (dark green) identified in Map 3, can be degraded by a number of factors.

For example, the physical barriers imposed by roads can have a significant impact on many species. Less obvious are other sources of stress such as noise, contaminated runoff, and lights. As primary habitats become sparse and degraded, it becomes necessary to identify secondary habitats.

Primary and potential secondary habitat

Secondary habitats that are adjacent to primary habitat act as buffers, reducing fragmentation and edge effects by increasing preserve size and sometimes increasing connectivity between individual habitats. They also provide resources for target species.

Land acquisition strategies seek to improve the quality of primary habitat and identify areas of potential secondary habitat. Life requirements are used to assess the quality of primary habitats and suitability of land cover conditions as secondary habitats. A resource protection plan that uses remote sensing can more clearly identify these areas and provide direction for planning and program implementation.

1. Chicago Wilderness. Chicago Wilderness, Exploring Nature and Culture. Fall 1999.

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